Copper-chlorine (Cu—Cl) cycle was identified as one of the promising lower temperature cycles to convert water into hydrogen and oxygen (Lewis et al., 2003; Serban et al., 2004). In particular, the CuCl cycle includes three chemical reactions to decompose water into hydrogen and oxygen. Two of the chemical reactions are thermal and one is an electrochemical reaction (Marin, 2012). The primary advantage of the Cu—Cl cycle is the low operating temperature (530° C.) compared to other thermochemical cycles. At this operating temperature, the CuCl cycle can be linked to Canada's Generation IV nuclear reactor, which is the CANDU Super-Critical Water Reactor (CANDU-SCWR).
The three reaction steps of the Cu—Cl cycle (see FIG. 1) are (Marin, 2012):2CuCl(a)+2HCl(g)→2CuCl2(a)+H2(g)100° C.  step (1)2CuCl2(s)+H2O(g)Cu2OCl2(s)+2HCl(g)375° C.  step (2)Cu2OCl(s)→2CuCl(l)+½O2(g)530° C.  step (3)where a, s, l and g denote aqueous, solid, liquid and gas respectively.
In the oxygen production step of the Cu—Cl cycle (Step 3), a solid copper oxychloride (Cu2OCl2), is decomposed thermally into oxygen gas (O2) and molten cuprous chloride (CuCl). The solid Cu2OCl2 is fed into an oxygen production thermolysis reactor from the CuCl2 hydrolysis reaction (Step 2) that operates at an average temperature of 375° C. The materials leaving the thermolysis reactor are oxygen gas and molten CuCl (which are evolved at a temperature of about 530° C.). In the thermolysis reactor, the decomposition of Cu2OCl2 to oxygen and molten CuCl is an endothermic reaction requiring a reaction heat of 129.2 kJ/mol and a temperature of 530° C., which is the highest temperature in the Cu—Cl cycle. Thus, heat must be added to increase the temperature of the slurry inside the thermolysis reactor. The total amount of heat required is the sum of reaction heat and the heat required to raise the reactant temperature from 375° C. (average temperature of solid particles from the hydrolysis reaction) to 530° C. (Naterer et al., 2008). However, there are some challenges that accompany the thermal design of the thermolysis reactor such as, but not limited to: the high temperature of the decomposition process (530° C.) and the large amount of heat that is required for the decomposition process in the thermolysis reactor.